Peaks & Valleys
It's like a Jaywalker crossed with a Broadripple, I think. =) The pattern is Peaks & Valleys Socks by Mountain Colors. Yarn is Claudia Hand Painted fingering weight in Just Plum.
I love this colorway--I think it looks very Koigu-ish but has a looser twist and feels softer to me. Also, the colorway is called "Just Plum" but I definitely see a lot of pink in there!